The present invention is directed to an implantable fixing means for extraoral applications.
For many years now, implantations have taken place of artificial ligaments, which link the parts of a human skeleton which are movable relative to one another. For example, in the case of damage or chronic instability of the crucial ligaments of the knee joint and when an intra-articular autologous reconstructions fails, it is possible to implant a set of crucial ligaments made from synthetic material. A special polytetrafluorethylene, which is sold under the trade name GORE-TEX, has proved suitable for this purpose because it is biologically inert and, therefore, particularly compatible with the body.
It has long been assumed that the fixing means for such artificial ligaments only plays a minor part because over the course of time they grow together with the endogenic tissue. However, it was found a certain time ago that the tissue reaction to the implantable crucial ligament sets differs widely so that it is not possible in all cases to assume a reliable growth of the artificial ligament into the endogenic tissue (See Ruston N. Dandy DJ, Naylor CPE. "The clinical, arthroscopic and histological findings after replacement of the anterior cruciate ligament with carbon-fibre". J. Bone Joint Surg (Br) 1983: 65-B: 308-9.) Thus, in many cases, the fixing means must fulfill their function for a long time in order, for example, to be able to withstand large forces which, even in the case of normal movement sequences, occurs in the knee joint.
Literature and practice provide numerous proposals for fixing or fastening of artificial ligaments. Apart from the conventional Sherman, special cortical screws have been developed for specific fixing loops. In addition, Richards clamps are used which may have barbs for insuring reliable seating in the previously-drilled bone. Bollard-like fixing means made from carbon fibre/polysulphone material have a split shank which is spread apart by knocking in a median pin. In addition, special implantable fixing members and in conjunction with cortical screws special through sleeves have been proposed (See article by Andrew A. Amis, "The strength of artificial ligament anchorages", J. Bone Joint Surg (Br) 1988: 70-B: 397-403).
Hitherto known fixing means for artificial ligaments are either very complicated with regard to their implantation or are not sufficiently stable to permanently withstand, without damage, the extremely high forces which can, for example, occur in the vicinity of the knee joint. Thus, there are constant deformations or even breaks in the fastening means or damage to the surrounding bone material which, in each case, makes further surgery necessary.
However, the fixing means for extraoral applications are not only required for artificial ligaments, but also in other fields.
In the case of serious cutaneous lesions, such as, for example, serious burns, it is necessary, for the avoidance of infection, to immediately cover the affected area with the suitable material. Particular problems are encountered with respect to a rapid and reliable fixing of the covering material because the destroyed areas are particularly sensitive to pressure and pain and, simultaneously, can have a marked plasticity and small surface area, for example in the facial area. No practical solution has heretofore been made for solving these problems.